Image via Vintage Postcards for the Holidays by Robert and Claudine Reed
This card, which was posted in 1931, depicts Santa's sleigh being pulled by eight reindeer. That started me wondering when Rudolph the Red-Nosed Reindeer first appeared; a quick Wikipedia search provided the answer: 1939, in a book published by the Montgomery Ward department stoer chain to be given away to their customers. Six millions copies were handed out over the next eight years, but the character didn't really take off (no pun intended) until 1949, when Johnny Marks (the brother-in-law of Robert L. May, the Montgomery Ward copywriter who created and eventually was given the rights to the character) wrote a song based on the story, which was subsequently recorded by Gene Autry. The Rankin-Bass television special was first broadcast in 1964 on NBC, though CBS now holds the broadcast rights.